Previous work has provided evidence that sodium cyanate and colchicine can inhibit circulation and metabolite uptake in hepatomas under conditions in which there is little or nor effect in normal tissues. The proposed research is aimed at increasing our understanding of the nature of compounds which can exert such effects and establishing conditions which will give maximum selective effects on neoplastic tissues. The action of organic isocyanates will be studied to see if they can influence metabolite uptake in tumors. Comparisons will be made between nitrosoureas with differing degrees of carbamoylating activity to determine if this activity can be related to inhibition of metabolite uptake. Preliminary studies on combination chemotherapy of murine melanoma will be extended to explore potential synergistic effects of cyanate with other agents. The potential value of cyanate in selective rescue protocols for cancer chemotherapy will be investigated.